All About Blood Type History

Sure, we all know that there are four main types of blood - A, B, AB, and O. But did you realize that blood types were only discovered in 1901?

Before this point, biologists could not understand why some transfusions worked and others didn't. Sometimes the patients lived, and sometimes they had bad reactions. In 1909, Karl Landsteiner in Vienna, Austria made the discovery that all blood is not alike. He won the Nobel Peace Prize for his work. There were four main 'groupings' of blood - A, B, AB and O - and they were not all compatible with each other.

Since then, over 300 blood types have been discovered, all falling into one of these four major groups. There are other factors like Rh Positive and Rh Negative. These other factors are not considered as important as the primary four, since normally just knowing the primary four allows you to safely perform a transfusion.